For the logistic differential equation dtdy=0.08y(30−y), the rate of change attains its maximum value when y=15. At which of the following population sizes is the instantaneous rate of change exactly one–half of this maximum?
a) Approximately 10 or 20
b) Approximately 7.5 or 22.5
c) Approximately 4.4 or 25.6
d) Approximately 12 or 18